/*-
 * <<
 * UAVStack
 * ==
 * Copyright (C) 2016 - 2017 UAVStack
 * ==
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * >>
 */

package com.creditease.uav.threadanalysis.server.da;

import java.util.Stack;

public class DeadlockCycle {

    private boolean[] marked;
    private int[] edgeTo;
    private Stack<Integer> cycle;
    private boolean[] onStack;

    public DeadlockCycle(ThreadDigraph g) {

        onStack = new boolean[g.vertex()];
        edgeTo = new int[g.vertex()];
        marked = new boolean[g.vertex()];
        for (int v = 0; v < g.vertex(); v++) {
            if (!marked[v]) {
                dfs(g, v);
            }
        }
    }

    private void dfs(ThreadDigraph g, int v) {

        onStack[v] = true;
        marked[v] = true;
        for (int w : g.adj(v)) {
            if (this.hasCycle()) {
                return;
            }
            else if (!marked[w]) {
                edgeTo[w] = v;
                dfs(g, w);
            }
            else if (onStack[w]) {
                cycle = new Stack<Integer>();
                for (int x = v; x != w; x = edgeTo[x]) {
                    cycle.push(x);
                }
                cycle.push(w);
                cycle.push(v);
            }
        }
        onStack[v] = false;
    }

    public boolean hasCycle() {

        return cycle != null;
    }

    public Iterable<Integer> cycle() {

        return cycle;
    }
}
